^^ i hate it how Nvidia is doing this. Renaming old cards. I think AMD is starting to do the same now, first is the RV790 being an OCed RV770.
Actually, RV790 is a different GPU to RV770.
RV790 is getting architectural tweaks, and it might be made on TSMC's GT process, instead of their GP process
Anyway, a different GPU name is not the same as what Nvidia has been doing.
Nvidia has 8800 series, 9600 series, 9800 series and now GTS 250's using G92 GPU's
RV770 and RV790 will both be 4800 series (RV790 = 4890)
I think basically the reason for Nvidia trying to use G92 in different card names, is to try and make it appear as though they have cards in between the G200 cards and the previous generation.
The fact is, G200 with its 512-bit bus is a very large die, and it's expensive to make. So it can't be used for anything but high-end cards (GTX 260). Otherwise, they'd be selling it at a loss.
RV770 using a 256-bit bus is a much smaller die and so AMD can afford to sell it cheaper (in the form of 4850 and 4830).
AMD/ATI can have cards at price points that Nvidia can't with G200. so, Nvidia attempt to cover it with G92.